Lipid Metabolism and Antioxidant Status in Sucrose vs. Potato-Fed Rats

Objective: Consumption of high levels of simple carbohydrates is associated with several metabolic disorders in humans and in laboratory animals, including symptoms of an early stage of metabolic syndrome (syndrome X). This disorder has several cardiovascular risk factors, such as hypertriglyceridemia, and is associated with an increase in oxidative stress. In contrast to sucrose, potato, a source of complex carbohydrates and antioxidant micronutrients, was thought to improve lipid metabolism and antioxidant protection.

Methods: We investigated the effects of diets containing i) complex dietary carbohydrates and antioxidant micronutrients (potato Solanum tuberosum L.), ii) complex carbohydrates (starch) and iii) a simple carbohydrate (sucrose) on lipid metabolism and antioxidant status in rats.

Results: An increase in short chain fatty acid (SCFA) pools was observed in the cecum of rats fed a potato-based diet, resulting from an increase in all SCFAs, especially propionate (+360%, P < 0.0001). Feeding rats a potato-based diet for 3 weeks led to a decrease in cholesterol (?37%, potato vs. control and ?32%, potato vs. sucrose) and triglycerides (?31%, potato vs. control and ?43%, potato vs. sucrose) concentrations in triglyceride-rich lipoproteins (TGRLP) fractions. The antioxidant status was decreased by sucrose consumption and improved by potato consumption.

Conclusions: Our present results suggest that consumption of complex carbohydrates (provided as cooked potatoes), in combination with different antioxidant micronutrients, may enhance the antioxidant defences and improve lipid metabolism, when compared with starch (complex carbohydrates) and to sucrose consumption (source of simple sugar). These effects limit oxidative stress and reduce the risk of developing the associated degenerative diseases, including cardiovascular disease, and could have potential in cardiovascular disease prevention.     

Influence of harvest date on nitrate contents of three potato varieties for off-season production

The influence of potato variety and harvest date was investigated on tuber nitrate content for off-season production in three varieties: Arinda (mid-early), Spunta (mid-late) and Mondial (late). Samples of tubers were harvested at 90, 105 and 120 days after planting in winter–spring crop and at 80, 95 and 110 days after planting in summer–autumn crop. Tuber nitrate content was determined by ion selective electrode (ISE) method. Investigated varieties differed in nitrate content. In both off-season crops, the highest quantities of nitrate were contained in the late Mondial, with respect to the middle early Arinda variety and Spunta. After a delay of the harvest date, nitrate contents in the investigated tuber samples significantly decreased in winter–spring crop, whereas they increased in summer–autumn crop in the three varieties, but to the greatest extent in the case of late Mondial variety. Regardless of variety and harvest time, the content of nitrate in tubers was within the guidelines proposed by some European countries.     

Phenolic content and antioxidant capacity of Philippine potato (Solanum tuberosum) tubers

Four potato (Solanum tuberosum) varieties – Bengueta, Ganza, Igorota and 125411.22 – were analyzed for total phenolic content and antioxidant activities to provide baseline data for Philippine potato varieties. Bengueta had the highest phenolic content with 50.0 ± 1.5 mg gallic acid equivalent (GAE)/100 g (dry basis, DB). It also had the highest DPPH radical scavenging activity with an EC₅₀ value of 30.6 ± 3.6 mg/mL (DB). The potato variety125411.22 had the highest reducing power with EC₅₀ equal to 66.2 ± 1.6 mg/mL (DB), while Igorota had the highest iron-chelating capacity with an EC₅₀ of 11.0 ± 3.2 mg/mL (DB) and the best inhibitory action against linoleic acid oxidation at 95.4 ± 2.2% at 50 mg/mL sample concentration. Methanolic potato extracts had better antioxidant activity than α-tocopherol and better iron chelating capacity than ethylenediamine tetraacetic acid (EDTA). Significant (^*P < 0.05) negative correlation (R = −0.542) was observed between total phenolic content and the EC₅₀ values for DPPH radical scavenging activity, but none between total phenolic content and reducing power, iron-chelating capacity and total antioxidant activity.     

Protein, iron, zinc and calcium concentrations of potatoes following traditional processing as “chuño”

Samples from unprocessed and processed cooked tubers of the nine most abundant potato cultivars used to prepare the traditional freeze-dried food product, “chuño” in the central highlands of Peru were prepared and analyzed for their protein and mineral concentrations. The protein, iron, zinc and calcium concentration of cooked chuño of the nine cultivars evaluated ranged from 0.49 to 1.15 g, from 0.29 to 0.65 mg, from 0.04 to 0.14 mg and from 18.9 to 31.0 mg per 100 g on a fresh weight basis, respectively. Potatoes processed as chuño have a lower concentration of protein and zinc than unprocessed tubers, and a higher content of calcium, while iron concentration may be expected not to be subjected to changes. Water used in preparing the chuño is suggested to be the cause for an increased calcium concentration in the final product, as the water used had higher calcium content before (1.35 mequiv./l) than after (0.84 mequiv./l) use in the preparation. Thus, water seems to be source of the increased calcium concentration.     

Influence of environment and genotype on polyphenol compounds and in vitro antioxidant capacity of native Andean potatoes (Solanum tuberosum L.)

The influence of environment and genetics on total phenolic content and hydrophilic antioxidant capacity (H-ORAC) of potato tubers was evaluated using 13 native Andean genotypes. Cultivars were grown at two highland locations in Peru: Huancayo and Huancani. Environmental conditions significantly affected the total phenolic contents and H-ORAC values in a cultivar-dependent manner. However, the potato genotype was the most determining factor of the observed variations. The effects of environment on individual phenolic compounds were also significant in terms of quantity, whereas the chemical profile remained stable across environmental conditions. To gain an insight into the observed antioxidant capacity of potato extracts, the individual and combined antioxidant effects of the main potato phenolic compounds were investigated. The ORAC values of reconstituted polyphenol mixtures reflecting the authentic phenolic composition of potato extracts were higher than expected from the summing of the ORAC values of individual phenolic compounds, indicating synergistic effects. The authentic potato extracts showed either a higher or a lower ORAC value than their reconstituted counterparts, suggesting positive or negative interactions with other compounds. Taken together, our results lead us to the following conclusions: (i) the hydrophilic antioxidant capacity observed in potato extracts is the result of various and complex interactions that could be attributed to phenolic compounds, to other non-identified molecules, and to synergistic as well as antagonistic effects between all these components and (ii) the high stability of the ranking of cultivars across environment in terms of phenolic content and antioxidant capacity indicates that the native Andean cultivars could be confidently used within breeding programs aiming at improving the health-promoting value of potato.     

Identification and quantification of phenolic compounds responsible for the antioxidant activity of sweet potatoes with different flesh colours using high performance thin layer chromatography (HPTLC)

The objectives of the present study were to develop a simple high performance thin layer chromatography (HPTLC)-based protocol: (i) to allow high-throughput profiling of phenolic compounds of microwaved roots from 295 sweet potato varieties and breeding lines, (ii) to quantify the content of anthocyanins and caffeoylquinic acid (CQA) derivatives, and (iii) to determine their respective contributions to the antioxidant activity of sweet potato methanolic extracts using the DPPH test. Analysed accessions were separated into three groups: white-fleshed (n = 100), orange-fleshed (n = 64) and purple-fleshed (n = 131). Purple-fleshed accessions presented the highest mean CQA content. After DPPH treatment and transmittance scanning of the plate at 517 nm, the most active free radical scavengers were found to be the four CQAs (CGA, 3,4-, 4,5- and 3,5-diCQA) while the anthocyanins were found to be less active. The total antioxidant capacity of the sweet potato methanolic extracts was mostly linked to total CQAs content. This method can now be used for fast routine analysis and selection of sweet potato breeding clones.     

The effect of frying on anthocyanin stability and antioxidant activity of crisps from red- and purple-fleshed potatoes (Solanum tuberosum L.)

Red- and purple-fleshed potatoes (Solanum tuberosum L.) are a good source of polyphenols, mainly anthocyanins as one of the most important components. The chemical composition with reducing sugars and the total polyphenol contents were analyzed in four purple potato varieties (Salad Blue, Vitelotte, Valfi, Blue Congo) and three red-fleshed potato varieties (Rosalinde, Herbie 26, Highland Burgundy Red). The anthocyanin composition of raw potato and potato crisps was characterized by high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) method. Moreover, the antioxidant activity was measured with the radical scavenging assays using 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical as well as ferric reducing ability of plasma assay (FRAP). In addition, colour parameters in prepared potato crisps were evaluated. Both red and purple-fleshed potato varieties contained high levels of total polyphenols (227–845 mg 100 g⁻¹ dry weight) and anthocyanins (21–109 mg 100 g⁻¹ dry weight). The process of frying caused degradation of anthocyanin compounds (38–70%). The HPLC–MS/MS analysis showed that pelargonidin and malvidin derivates were more stable during frying than petunidin derivatives. Although frying process affected the anthocyanin and polyphenol levels, obtained potato crisps exhibited bright intensive colour and good antioxidant activity.     

Potato genotype differences in nutritionally distinct starch fractions after cooking, and cooking plus storing cool

Rapidly digestible (RDS), slowly digestible (SDS) and resistant starch (RS) were measured in 9 New Zealand supermarket potatoes and in 37 lines from a potato breeding program by in vitro digestion immediately after cooking, and after storing at 4 °C for 44 h post-cooking. The aim was to measure the range in the tendency to form SDS and RS in the potato gene pool in New Zealand. Immediately after cooking, the potatoes contained (mean and across-cultivar range, dry matter basis) 68% RDS (range 62–73%), 3% SDS (range 0–8.5%), and 3.9% RS (range 3–6.4%). Cool storage after cooking altered the distribution and ranges to 44% RDS (range 33–53%), 23% SDS (range 15–34%) and 7% RS (range 4.7–15.8%). There was no significant relationship between RS and SDS in the cooked-cooled potatoes. In the 37 potato lines, SDS ranged from 7 to 37% of total starch, RS from 12 to 27% of total starch after the post-cooking cool treatment. The results suggest that the glycaemic impact of some potatoes may be substantially reduced by cool-storing after cooking, and that the differences between cultivars in the tendency to form cold-induced SDS and RS are sufficient for these traits to be used in conventional plant breeding.     

Application of multidimensional scaling technique to differentiate sweet potato (Ipomoea batatas (L.) Lam) cultivars according to their chemical composition

Proximate composition (moisture, protein, starch, amylose, total dietary fibre, Brix degree, fat, ash, ascorbic acid, phenolic compounds, acidity and pH), minerals (Na, K, Ca, Mg) and trace elements (Fe, Cu, Mn, Zn) were determined in 30 cultivars of sweet potato from the Canary Islands (Spain). There were significant differences between the sweet potato cultivars for all the parameters studied; in addition, both the island of production and the cultivation cycle showed a noteworthy influence on the mineral and trace element composition of the tubers. It is worth mentioning that the consumption of sweet potatoes contributes relatively high intake levels of vitamin C, phenolic compounds and mineral and trace elements (K, Mg, Ca, Mn, Fe and Cu). Application of multidimensional scaling (MDS) correctly classified the sweet potato cultivars according to the island of production and maturation cycle.     

Phenotypic, agronomic and nutritional characteristics of seven varieties of Andean potatoes

Potatoes are part of the staple food of Andean populations. Although there are more than 200 Andean potato varieties, only a few are cultivated at present, which endangers the biodiversity of the region. The objective of this paper was to characterize seven varieties of Andean potatoes (Collareja, Runa, Churqueña, Señorita, Imilla Colorada, Imilla Negra and Revolución) and to determine their phenotypic, functional and nutritional properties. The different varieties of Andean potatoes show differences in their agronomic properties, such as area of production and altitude yield per hectare, pest resistance and sowing and harvesting seasons. They are adapted to different altitudes, which influence their agronomic characteristics. Yield varies between 8000 and 18,000 kg/ha according to the variety. They present a diversity of forms, sizes and colors. The energy content ranges from 315 to 424 kJ/100 g, with these values being higher than those of the reference variety (239 kJ/100 g). Vitamin C content ranges from 10.5 mg/100 g found in Revolución varieties to 15.6 mg/100 g in Collareja potatoes; the vitamin C content in Spunta lies within this range (13.3 mg/100 g of potato). Increased knowledge of the nutritional, agronomic and functional properties of Andean potato varieties will contribute to the preservation of a biodiversity that is part of Argentina's regional heritage.     

The influence of RS4 resistant starch on wistar rats metabolism. Biochemical and lipid indices

The influence of resistant starch RS4 on total cholesterol (TC), HDL cholesterol, triacyloglycerols (TAG) composition in blood serum and liver of rats was determined. 4 week experiment involved 32 males and 40 females laboratory Wistar rats allotted in 4 groups in each sex. Control rats were feed ad libitum with standarised synthetic diet AIN-93. In experimental groups animals were given modified feed enriched with 5% of resistant starch. monophosphate of potato starch, monophosphate of soluble potato starch and monophosphate of potato starch heated with glycne and microwaved were examined. Diet enrichment with resistant starch decerased triacyloglycerol level (TAG) while the total cholesterol (TC) level, in serum was not affected.     

甘薯抗氧化物的分离提取及其生物活性研究

目的:研究甘薯中抗氧化物质的含量,化学成分,分离提取及其生物活性。方法:采用乙醇提取,AB-8大孔树脂吸附纯化方法分离提取甘薯抗氧化物质;通过测定清除超氧阴离子自由基_?O2及·OH的能力及小鼠体内SOD活性等分析其抗氧化能力。结果:甘薯的块根、蔓和叶中均含有抗氧化物质,其含量在组织和品种间有明显差异,最高的品种含量可达0.324%,并且主要分布在甘薯块根中,占总含量的70%以上,提取率达85%以上;初步确定甘薯抗氧化物的主要成分是酚酸类物质,其中包括绿原酸、异绿原酸、新绿原酸和4-O-咖啡酰奎尼酸;当甘薯抗氧化物浓度为90mg/ml时,对_?O2和·OH的清除率分别为88.02%和82.21%;能抑制由·OH引发的脂质过氧化及由H2O2诱导的红细胞氧化溶血;能提高小鼠血清及皮肤细胞中SOD的活性。结论:甘薯中含有较多的酚酸类抗氧化物质,并具有体内外抗氧化活性。     

Nutrient utilisation and intestinal fermentation are differentially affected by the consumption of resistant starch varieties and conventional fibres in pigs

This study examined the influence of different resistant starch (RS) varieties and conventional fibres on the efficiency of nutrient utilisation and intestinal fermentation in pigs. Thirty-six pigs (30 kg) were fed poultry meal-based diets supplemented with 10 % granular resistant corn starch (GCS), granular resistant potato starch (GPS), retrograded resistant corn starch (RCS), guar gum (GG) or cellulose for 36 d according to a completely randomised block design. Distal ileal and total tract recoveries were similar (P>0.05) among the RS varieties. Distal ileal starch recovery was higher (P < 0.05) in pigs consuming the RS diets (27-42 %) as compared with the control group (0.64 %). Consumption of GCS reduced (P < 0.05) apparent total tract digestibility and whole-body retention of crude protein in comparison with the control group. Consumption of GPS reduced (P < 0.05) total tract Ca digestibility and whole-body retention of Ca and P compared with the control group. However, consumption of RCS increased (P < 0.05) total tract Ca digestibility compared with the control group. Caecal butyrate concentration was increased (P < 0.05) following consumption of RCS and GG in comparison with the control group. Consumption of all the RS varieties reduced (P < 0.05) caecal indole concentrations compared with the control. Caecal butyrate concentrations were positively correlated (P < 0.05; r 0.63-0.83) with thermal properties among the RS varieties. We conclude that nutrient utilisation and intestinal fermentation are differentially affected by the consumption of different RS varieties and types of fibres. Thermal properties associated with different RS varieties may be useful markers for developing RS varieties with specific functionality.     

Digestibility of native and modified starches: in vitro studies with human and rabbit pancreatic amylases and in vivo studies in rabbits

The effects of cooking and chemical modification of purified starches on the relative rates and extent of their hydrolysis were studied in vitro by using purified human and rabbit pancreatic amylases. Comparison was made with an in vivo study of postprandial glucose and insulin response in adult rabbits. Uncooked starches showed negligible hydrolysis in vitro, whereas cooking (10 min, 100 degrees C) increased both the rate and extent of hydrolysis of all starches. Soluble potato starch was the most and potato amylose the least hydrolyzed. Unmodified tapioca and waxy corn starch were hydrolyzed at the same rate and to the same extent as soluble potato starches. In most cases chemical modification did not change the rate and extent of hydrolysis of the starches. Minor differences between human and rabbit pancreatic amylase exist, but there is a general resemblance between the two amylases in their starch-hydrolyzing properties (correlation coefficient = 0.90; P less than 0.001). The in vivo study showed that uncooked starches elicited no detectable glucose and insulin responses, whereas all the cooked starches except amylose caused glucose and insulin responses comparable to the response seen when feeding glucose. Chemically modified starches (especially waxy corn acetylated distarch adipate) seemed to promote a faster rate of absorption, but the total glucose response (i.e., for the entire 180-min duration) was similar for modified starches and their unmodified counter-parts. The in vivo results showed an overall qualitative similarity to the in vitro results but presented a quantitative difference in the magnitude of the responses for various starch preparations. A good correlation exists between the in vitro and in vivo results (correlation coefficient = 0.84; P less than 0.01). This indicates that the action of pancreatic amylases is an important determinant in the digestion and absorption of these carbohydrates.     

食物中的抗性淀粉含量及烹调加工的影响

目的:分析不同烹调、加工方式对食物中抗性淀粉含量的影响,为从饮食上指导和预防结肠癌等慢性病的发生提供科学依据。方法:将六类高碳水化物的食物按北方居民日常饮食进行烹饪,采用体外模拟胃肠道酶解法对食物烹调前后的抗性淀粉及总淀粉进行测定。结果:抗性淀粉的含量在食物烹调前后除豆类无明显变化外,所占比例均明显降低,不同的加工及烹调方式对抗性淀粉的影响也不相同。生食物中以薯类及薯芋类蔬菜的抗性淀粉比例较高(24.82~46.06g/100g总淀粉),其次是大米和玉米,面粉、豆类、根茎类蔬菜含量较低。熟食中以油炸土豆片(29.11±1.52g/100g总淀粉)最高,其次为红小豆(17.29±2.30g/100g总淀粉)。结论:体外模拟胃肠道酶解法测定食物中抗性淀粉与回肠造口术的体内数据有较好的一致性,不同烹调加工方式能够影响食物中的抗性淀粉含量。     

Diversity in composition of scarlet (S. aethiopicum) and gboma (S. macrocarpon) eggplants and of interspecific hybrids between S. aethiopicum and common eggplant (S. melongena)

Scarlet (Solanum aethiopicum) and gboma (S. macrocarpon) eggplants are cultivated vegetable crops native to Africa, for which no comprehensive reports exist on composition and diversity. We have evaluated diversity in composition of three varieties of scarlet eggplant and four varieties of gboma eggplant, as well as of four interspecific hybrids between scarlet and common eggplant (S. melongena) and their respective parents. With the exception of moisture (between 85.8 and 88.3 g/100 g) and pH (between 5.32 and 5.89), there was a wide diversity among varieties within each of the species for the composition traits evaluated, revealing ample possibilities for selection of varieties with improved fruit composition. Scarlet eggplant varieties evaluated presented, on average, lower content than gboma eggplant varieties for carbohydrates (3.60 vs 6.48 g/100 g), starch (3.18 vs 6.15 g/100 g), vitamin C (11.6 vs 18.9 mg/100 g), and total phenolics (24.4 vs 144 mg/100 g) and higher values for soluble sugars content and for the ascorbic/dehydroascorbic acid ratio. Interspecific hybrids between scarlet and gboma eggplants presented moisture content (79.0 g/100 g) and pH (5.15) values below those of any of the parents. For the rest of traits, values were intermediate between both parents, although much more similar to the scarlet eggplant parent.     

Effects of two fermentable carbohydrates (inulin and resistant starch) and their combination on calcium and magnesium balance in rats

Resistant starch and inulin are complex carbohydrates that are fermented by the microflora and known to increase colonic absorption of minerals in animals. The fermentation of these substrates in the large bowel to short-chain fatty acids is the main reason for this increase in mineral absorption. The purpose of the present study was to examine the potential synergistic effect of a combination of these two fermentable carbohydrates. For this purpose, thirty-two adult male Wistar rats weighing 200 g were used in the present study. The rats were distributed into four groups, and fed for 21 d a fibre-free basal purified diet or diet containing 100 g inulin, or 150 g resistant starch (raw potato starch)/kg diet or a blend of 50 g inulin and 75 g resistant starch/kg diet. After an adaptation period of 14 d, the rats were then transferred to metabolic cages and dietary intake, faeces and urine were monitored for 5 d. The animals were then anaesthetized and caecal Ca and Mg absorption were measured. Finally, the rats were killed and blood, caecum and tissues were sampled. Ca and Mg levels were assessed in diets, faeces, urine, caecum and plasma by atomic absorption spectrometry. Our results confirmed that inulin and resistant starch ingestion led to considerable caecal fermentation in the three experimental groups compared with the control group diet. Moreover, both carbohydrates significantly increased the intestinal absorption and balance of Ca and Mg, without altering the plasma level of these two minerals. Interestingly, the combination of the studied carbohydrates increased significantly the caecal soluble Ca and Mg concentrations, the apparent intestinal absorption and balance of Ca, and non-significantly the plasma Mg level. In conclusion, a combination of different carbohydrates showed synergistic effects on intestinal Ca absorption and balance in rats. Further studies with other types of carbohydrate combinations should be carried out to extend these findings.     

Ascorbic acid concentration of native Andean potato varieties as affected by environment, cooking and storage

The ascorbic acid (AA) concentration of tubers was determined in 25 Andean potato varieties (Solanum tuberosum L.) grown in three environments, and the effect of cooking and storage time in subsets of samples was evaluated. Significant variation due to genotype, environment and genotype × environment (G × E) interaction was found. AA concentration in freshly harvested raw, peeled tubers ranged from 22.2 to 121.4 mg/100 g on a dry weight basis (DW) and from 6.5 to 36.9 mg/100 g on a fresh weight basis (FW) with the accession 704393 showing the highest levels of AA in all three locations. Differences in AA concentration were found among cooking methods and storage times; and significant non-crossover interactions with genotype were observed for both of these parameters. It was found that AA concentration of boiled tubers of the six varieties evaluated was higher than in oven and microwaved tubers and that AA concentration of tubers of the 23 varieties evaluated decreased with storage time. The variety 704393 retained 54 and 34% of its original AA concentration after boiling and storage during 26 weeks under farmer conditions. One hundred grams of fresh harvested boiled potatoes of this variety (704393) could provide adults with 17–20% of the recommended daily allowance (RDA) of AA.     

Variation among highbush and rabbiteye cultivars of blueberry for fruit quality and phytochemical characteristics

Variability in soluble solids (SS), titratable acidity (TA), SS/TA, pH, total phenolic content (TPC), ferric reducing ability of plasma (FRAP), total monomeric anthocyanin content (TMAC) and levels of vitamin C were evaluated in a broad array of northern and southern highbush (Vaccinium corymbosum) and rabbiteye (Vaccinium virgatum) cultivars of blueberry, grown in different locations and years. When cultivars were grouped by decade of release, there were few significant overall trends observed over years in fruit quality and phytochemical content; however, individual cultivars varied significantly for all the traits analysed. Considerable overlap in most quality and phytochemical characteristics were found among cultivars of the three blueberry types, suggesting that genetic barriers do not exist among the various types of blueberries with regard to breeding cultivars with comparable sugar, acid and phytochemical properties. There were significant negative correlations observed between fruit weight and SS, TPC, FRAP and TMAC, suggesting that as breeders have been selecting for larger fruit, they have inadvertantly selected for tarter fruit with lower antioxidant capacity. However, SS was correlated positively with FRAP and TMAC, indicating that cultivars can be developed that have high antioxidant capacity and anthocyanin content, combined with high sugar content.